There is an immense interest in the fabrication of new carbon-based nanomaterials with highly curved graphitic structures. The interest in these materials stems from their unique structural, mechanical and electronic properties, and hence their potential for use in important commercial products. These materials, which include open and closed nanotubes, carbon onions and graphitic nanocones, are mostly synthesized, typically in low yield, via laser vaporization, resistive heating or arc discharge methods, usually under high vacuum. See, for example, Iijima, S. Nature, 1991, 354, 56; Ugarte, D. Nature, 1992, 359, 707; and Krishnan, A.; Dujardin, E.; Treacy, M. M. J.; Hugdahl, J.; Lynum, S.; Ebbesen, T. W. Nature, 1997, 388, 451, which literature references are incorporated herein by reference. Furthermore, the products of such conventional syntheses are often heterogeneous, typically being mixed with large amounts of undesirable materials and therefore being difficult or impossible to purify. See, for example, Georgakilas, V.; Voulgaris, D.; Vázquez, E.; Prato, M.; Guldi, D. M.; Kukovecz, A.; Kuzmany, H. J. Am. Chem. Soc. 2002, 124, 14318 which literature reference is incorporated herein by reference. New and improved methods for the fabrication of carbon nanoparticles would be especially welcome if they could produce samples of both high purity and yield from readily available, renewable, inexpensive and benign starting materials.
Cellulose is unique among biopolymers in that, when it is charred below 400° C. and above its decomposition temperature of 280° C., it produces an aromatic structure in which domains of polycyclic aromatic hydrocarbon (PAH) anneal during such a charring step into larger ensembles of five- and six-membered aromatic rings. See, for example, Herring, A. M.; McKinnon, J. T.; Petrick, D. E.; Gneshin, K. W.; Filley, J.; McCloskey, B. D. J. Annal. Appl. Pyrol. 2003, 66, 165, which literature reference is incorporated herein by reference. Other biopolymers, such as pectin, xylan and lignin, also produce chars containing aromatic structure, but these other biopolymers do not exhibit this PAH annealing behavior on charring to the same extent as does cellulose. The extensive hydrogen bonding network between the decomposing cellulose strands almost certainly plays an important role in this behavior. The decomposition of cellulose has been studied extensively, primarily for the purposes of understanding biomass energy processes, but cellulose has not previously been used for nanomaterial synthesis.
Nanoparticles previously have been produced from aromatic and PAH molecules and carbon soot, for example via catalyzed or templated routes. See, for example, Boese, R.; Matzanger, A. J.; Volhardt, K. P. C. J. Am. Chem. Soc. 1997, 119, 2052; Goel, A.; Hebgen, P.; Vander Sande, J. B.; Howard, J. B. Carbon 2002, 40, 177; Hou, H.; Schaper, A. K.; Weller, F.; Greiner, A. Chem. Mater. 2002, 14, 3990; Hu, G.; Ma, D.; Cheng, M.; Liu, L.; Bao, X. Chem. Commun. 2001, 8630; and, Gherghel, L.; Kübel, C.; Lieser, G.; Räder, H.,-J.; Müllen, K. J. Am. Chem. Soc. 2002, 124, 13130, which literature references are incorporated herein by reference. These methods are not well understood, but are strongly influenced by the presence or absence of either a catalyst or a template species. Similar structures, with a diameter of ca. 100 nm, have been prepared by annealing carbon onions, produced by autoclave reaction of NaCl and hexachloro benzene, at 1400° C. In these experiments, the NaCl is intercalated in the graphitic layers of the carbon onions, and the vaporization of this salt results in the larger hollow carbon nanospheres.
Thus, carbon nanoparticles prepared in various ways and with many morphological structures have existed prior to the current invention. The current technology in this field, however, is deficient or inadequate in one or more of the following ways:                1. Expensive processing operations to create the nanoparticle products.        2. Expensive materials or catalysts required to create the nanoparticle products.        3. Nanoparticle products are produced in low yields.        4. Nanoparticle products are produced in low purity.        5. Nanoparticle products are difficult or impossible to obtain in pure form.        6. Nanoparticle products are not in the best morphological configurations for use in the desired applications.        
These and other deficiencies in or limitations of the prior art are overcome in whole or at least in part by the apparatus and methods of this invention.